In chemical vapor deposition (CVD) processes, including epitaxial growth processes, uniformity in the thickness of a deposited film on a substrate is dependent on, among other factors, uniformity in the flow distribution of gasses within the process chamber. As the requirements for uniformity in film thickness become more stringent, the desire for more uniform flow rate distribution of gasses in the process chamber increases.
In conventional CVD devices, a source gas is introduced into the process chamber through a set of liners. Conventional liners include an upper fluid guide and a lower fluid guide that guide gas over the top surface of the substrate without disturbing its distribution to the extent possible.
However, the fluid guides of conventional liners are stepped or linearly sloped. In particular, the upper fluid guide is typically stepped and the lower fluid guide is typically stepped or linearly sloped. As a result, the fluid guides disturb the incoming gas flow such that the gas flow rate at certain regions on the substrate surface are significantly higher than others, resulting in uneven growth rates. This results in a non-uniform film thickness. These negative effects are amplified at higher flow rates, which are desirable to increase the throughput of CVD devices.
The fluid guides of conventional liners can also disturb the incoming gas flow such that little gas flows over certain regions of the substrate surface, resulting in “dead spots” on the substrate surface.
Additionally, because stepped and linearly sloped fluid guides of conventional liners disturb the incoming gas flow, the flow rate distribution across the substrate surface is highly dependent upon the incoming gas flow rate and gas type. As a result, when the gas flow rate or gas type is changed, the CVD device must be tuned by varying one or more parameters of the CVD reactor to account for changes in the flow rate distribution across the substrate surface.
A need exists for a liner assembly capable of delivering a more uniform flow rate distribution across the surface of a substrate.
This Background section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.